Question

The process that you saw in Activity 14.7 is used for purification of copper.
A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transfered to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?​

Answer 1

Answer:

Copper ions are positively charged. They are attracted towards the plate which is connected to the negative terminal of the battery. As copper ions are transferred to the thin copper plate, this thin pure copper plate must be connected to the negative terminal of the battery. Consequently, impure copper rod is connected to the positive terminal of the battery.

When electric current is passed in this arrangement, copper ions from the solution get deposited on pure copper rod (attached to negative terminal) and copper ions from impure copper rod (attached to positive terminal) are liberated into the solution.

Answer 2

Answer:

The thick rod of impure copper plate is to be attached to the positive terminal of the battery because when electric current is passed through the copper sulphate solution, it gets dissociated into copper and sulphate. The free copper, being positively charged, gets drawn to the negative terminal of the battery and gets deposited on it. On the other hand the loss of copper from the solution is regained from the impure copper rod which is attached to the positive terminal of the battery.